1. Field of the Invention
The invention relates generally to electromagnetic positioning means or actuators. More particularly, it relates to a novel method of activating an electromagnetic actuator and to an apparatus or system for carrying out the method.
In the context of this invention, an electromagnetic actuator is understood to mean a device which comprises a positioning member which in its passive or inactive condition assumes a rest position under the bias of two counteracting springs, between first and second terminal positions. Affixed to the positioning member is an armature which is movable by two electromagnets. The armature, together with the positioning member and the two springs, comprises a vibratory or oscillatory system in the nature of an electrical cam. It may be moved into the first terminal position by one of the electromagnets against the bias of one of the springs, and it may be moved into the second terminal position, against the bias of the other spring, by the other electromagnet.
2. Description of the Prior Art
German published Patent Specification No. P 26 30 512 teaches an electromagnetic actuator of the kind here under consideration. That is to say, the actuator comprises a positioning member which when in its inactive condition assumes a rest position intermediate first and second terminal positions, and it is maintained in this rest position by the bias of two counteracting springs. Affixed to the positioning member is a magnetizable armature which cooperates with two electromagnets for moving the positioning member between its first and second terminal positions. Hence, the armature, together with the positioning member and the two springs, constitutes a vibratory or oscillatory system. It is movable into its first and second terminal positions, respectively, against the bias of one or other of the springs, by energizing the appropriate one of the electromagnets. The electromagnets are provided with appropriate abutment faces. Nothing is said in the specification in respect of the manner in which the device is switched from its inactive condition in which the armature rests intermediate the electromagnets, into its activated condition in which the armature would be in engagement with one of the electromagnets. Activation by energizing one of the electromagnets requires currents of considerable strength, for on the one hand there exists quite a large gap between the armature and the electromagnet before its energization, and on the other hand the force of the associated spring has to be overcome.
For activating such a positioning means there is disclosed in German published Patent Specification DE-OS No. P 30 24 109 a cocking or winding device by means of which the locus of the rest position may by changed in such a manner that the armature connected to the positioning member is moved into engagement with one of the electromagnets so that the positioning member upon activating the electromagnet remains in engagement therewith when the cocking device is turned off. With the armature in engagement with one of the electromagnets the actuator is in an activated state and can only be moved into its terminal positions by energization of the electromagnets. The cocking or winding device disclosed in the specification requires considerable space and significantly adds to the cost of the device.
German published Patent Specification DE-OS No. P 28 15 849 relates to an electromagnetic valve control means for internal combustion engines. The control means is provided with a single electromagnet which in its energized state attracts the armature connected to a valve member, thus moving the valve into its open condition, against the force of a closing spring. For energizing the electromagnet, means is provided for generating a square wave voltage signal. As will be apparent to those skilled in the art, relatively strong currents and considerable electrical energy are required in such valve controls to generate the force necessary for opening the valve.